Essential Concepts in Chemistry, Cell Biology, and Membrane Transport for Anatomy & Physiology

Review of General Chemistry

Atom

The atom is the fundamental unit of matter, composed of subatomic particles that determine its chemical properties.

• Nucleus: Contains protons (positively charged), neutrons (neutral), and is surrounded by electrons (negatively charged).

• Atomic Number: Number of protons in the nucleus; defines the element.

• Atomic Mass: Sum of protons and neutrons in the nucleus.

• Isotopes: Atoms of the same element with different numbers of neutrons.

Ions

Ions are atoms or molecules that have gained or lost electrons, resulting in a net charge.

• Atomic Structure: Electrons are arranged in energy levels (shells) and orbitals.

• Octet Rule: Atoms tend to gain, lose, or share electrons to achieve eight electrons in their outer shell.

• Common Orbitals: 1s, 2s, 2p, 3s, 3p, 4s, 3d

Electron Configurations (Bohr Model)

Electron configuration describes the arrangement of electrons in an atom's shells and subshells.

• Electrons fill orbitals in order of increasing energy.

• Bohr model visualizes electrons in discrete energy levels.

Lewis Dot Structures

Lewis dot structures represent valence electrons around atoms and show bonding in molecules.

• Dots represent valence electrons.

• Helps predict molecular shape and reactivity.

Ionic Bonding

Ionic bonds form between atoms that transfer electrons, resulting in oppositely charged ions.

• Example: NaCl (sodium chloride)

Covalent Bonding

Covalent bonds form when atoms share electrons to achieve stability.

• Example: H2O (water)

Chemistry of Carbon (Organic Chemistry)

Carbon forms the backbone of organic molecules due to its ability to form four covalent bonds.

• Hydrocarbons: Compounds composed of only carbon and hydrogen.

• Carbon Skeleton: The arrangement of carbon atoms in a molecule determines its shape and function.

• Functional Groups: Specific groups of atoms that confer particular chemical properties.

Functional Group	Structure
Hydroxyl	HO-
Aldehyde	COH-
Carbonyl (ketone)	CO-
Carboxyl	COOH-
Amine	NH2
Phosphate	H2PO4-
Sulfhydryl	SH-
Methyl	CH3-

• Bond Energy: The energy required to break a chemical bond.

pH

pH measures the concentration of hydrogen ions in a solution, indicating its acidity or alkalinity.

• pH scale ranges from 0 (acidic) to 14 (basic), with 7 being neutral.

• $pH = -\log[H^+]$

Cell Biology

Cells

Cells are the basic units of life, classified by structure and function.

• Eukaryotic: Cells with a nucleus and membrane-bound organelles.

• Prokaryotic: Cells without a nucleus; bacteria and archaea.

• Heterotrophic: Obtain energy from organic compounds.

• Autotrophic: Produce their own energy (e.g., photosynthesis).

Cell Membrane

The cell membrane regulates the movement of substances in and out of the cell.

• Fluid-Mosaic Model: Describes the membrane as a dynamic structure with proteins, cholesterol, and glycoproteins/lipoproteins embedded in a phospholipid bilayer.

• Membrane-Mediated Transport: Includes endocytosis (uptake of materials) and exocytosis (release of materials).

• Other Structures: Cilia, flagella, basal bodies, microvilli.

Cytoplasm

The cytoplasm is the gel-like substance within the cell, containing organelles and cytoskeleton.

• Cytoskeleton: Provides structural support; includes microtubules and microfilaments.

Cell Organelles

Organelles perform specialized functions within the cell.

• Nucleus: Contains DNA, chromosomes, chromatid, chromatin, and genes.

• Mitochondria: Site of cellular respiration and energy production.

• Golgi Body: Modifies, sorts, and packages proteins.

• Endoplasmic Reticulum: Rough (with ribosomes) and smooth (lipid synthesis).

• Lysosomes: Digestive organelles.

• Peroxisomes: Break down fatty acids and detoxify harmful substances.

Genetics and Molecular Biology

Cell Nucleus

The nucleus stores genetic material and coordinates cellular activities.

• Chromosomes and Genes: DNA is organized into chromosomes; genes are segments coding for proteins.

• Nucleic Acids: DNA and RNA are polymers of nucleotides.

• Nucleotides: Purines (Adenine, Guanine), Pyrimidines (Cytosine, Thymine, Uracil).

Base Pairing	DNA	RNA
Adenine	T	U
Guanine	C	C
Cytosine	G	G
Thymine	A	A

• DNA Structure: Double helix, antiparallel strands, sugar-phosphate backbone.

• RNA Structure: Single-stranded, ribose sugar.

DNA Replication (Semiconservative)

DNA replication ensures genetic information is accurately copied for cell division.

• Daughter strands are synthesized in the 5' to 3' direction.

• Leading strand: synthesized continuously.

• Lagging strand: synthesized discontinuously (Okazaki fragments).

• DNA polymerase: enzyme that synthesizes new DNA.

• Mutations: errors in replication.

Protein Synthesis

Protein synthesis involves transcription and translation, converting genetic information into functional proteins.

• Transcription: DNA is transcribed to mRNA in the nucleus.

• Translation: mRNA is translated into a polypeptide at the ribosome.

• Codons: Three-nucleotide sequences in mRNA specify amino acids.

• tRNA: Transfers amino acids to the ribosome.

• Ribosome: Site of protein synthesis.

Example:

DNA (nonsense strand)	mRNA	Peptide
5' ATG CGA GTA 3'	5' AUG CGA GUA 3'	met pro val

Genetics

Genetics studies inheritance patterns and gene expression.

• Autosomal vs. Sex-linked: Autosomal genes are on non-sex chromosomes; sex-linked genes are on sex chromosomes.

• Dominant vs. Recessive: Dominant alleles mask recessive alleles.

• Exceptions to Mendelian Genetics: Includes incomplete dominance, codominance, and polygenic inheritance.

Membrane Transport

Vesicular-Mediated Transport

Transport of large molecules via vesicles.

• Endocytosis: Uptake of materials (pinocytosis: fluids; phagocytosis: particles).

• Receptor-Mediated Endocytosis: Specific uptake via receptors.

• Exocytosis: Release of materials from the cell.

Simple Diffusion

Movement of molecules from high to low concentration without energy input.

• Depends on concentration gradient, membrane permeability, surface area, and temperature.

Facilitated Diffusion

Passive transport of molecules via membrane proteins.

• Requires hydrophilic core and specific receptors.

Active Transport

Movement of molecules against the concentration gradient using energy (ATP).

• Requires membrane proteins and energy input.

Osmosis

Osmosis is the diffusion of water across a selectively permeable membrane.

• Water moves toward higher solute concentration.

• Osmotic pressure: pressure required to prevent water movement.

• $\text{Osmotic Pressure} = iMRT$

Additional Prerequisite Topics

• Membrane transport: Includes osmosis and solution calculations.

• Biochemistry: Study of chemical processes in living organisms.

• Metabolism: Sum of all chemical reactions in the cell.

Additional info: These notes provide foundational knowledge required for success in Anatomy & Physiology, especially in biochemistry and cell biology.